# [Record] How to build and use static library and dynamic library in linux
###### tags: `static library`,`dynamic library`, `.so`, `compile`, `link`
[toc]
## Preface
Here, we are going to demo how to build or create a static library and a dynamic library, and how to use them with our application.
Asume we want to access a register by reading or writing it.
First, we implement the library which includes a get and set function. The get function will read a value from a file, and the set function will set a value to the file. The value of a register is stored in a file. Second, we implement the application to call API from this library.
Finally, we compile both the library and application and link them them together.
## Git repo
https://github.com/anderson-tomas/demo_library
## Source code
### File tree
The library is named regapi with a c file and a header as shown below. And the application is named main.c.
### Library
We declare a global and two functions which are get and set.
```c
Tomas# cat regapi/include/regapi.h
#ifndef __REGAPI_H__
#define __REGAPI_H__
#include <stdio.h>
#include <stdlib.h>
#define REG_FILE "reg.txt"
int regget();
void regset(int x);
#endif
Tomas# cat cat regapi/src/regapi.c
#include "regapi.h"
int regget() {
FILE *file = fopen(REG_FILE, "r"); // Open the file for writing
char buffer[1024];
if (file == NULL) {
perror("Error opening the file");
printf("Call %s to get the default reg value 666\n", __func__);
return 1;
}
// Read the string from the file
if (fgets(buffer, sizeof(buffer), file) != NULL) {
printf("Call %s to get reg value %s\n", __func__, buffer);
}
// Close the file
fclose(file);
return atoi(buffer);
}
void regset(int val) {
FILE *file = fopen(REG_FILE, "w"); // Open the file for writing
if (file == NULL) {
perror("Error opening the file");
return;
}
printf("Call %s to set reg value %d\n", __func__, val);
// Write the string to the file
fprintf(file, "%d", val);
}
```
### Application
```c
Tomas# cat main.c
#include <stdio.h>
#include <stdlib.h> // Include for atoi
#include <string.h> // Include for strcmp
#include "regapi.h"
int main(int argc, char *argv[]) {
if (argc < 2) {
printf("Usage: %s [get | set <value>]\n", argv[0]);
return 1;
}
if (strcmp(argv[1], "get") == 0) {
printf("get reg value: %d\n", regget());
} else if (strcmp(argv[1], "set") == 0) {
if (argc < 3) {
printf("Usage: %s set <value>\n", argv[0]);
return 1;
}
int value = atoi(argv[2]);
printf("set reg value to %d\n", value);
regset(value);
} else {
printf("Invalid command. Usage: %s [get | set <value>]\n", argv[0]);
return 1;
}
return 0;
}
```
## Static library
1. Compile the regapi.c to an object by gcc.
```shell
Tomas# gcc -c regapi/src/regapi.c -Iregapi/include/
Tomas# ls -al regapi.o
-rw-rw-r-- 1 tomas tomas 3088 十 22 19:53 regapi.o
```
2. Create a static library and replace the object by ar.
```shell
Tomas# ar rcs libregapi.a regapi.o
Tomas# ls -al libregapi.a
-rw-rw-r-- 1 tomas tomas 3242 十 22 19:55 libregapi.a
```
3. Check symbols in library by nm
```shell
Tomas# nm libregapi.a
regapi.o:
U atoi
U fclose
U fgets
U fopen
U fprintf
0000000000000091 r __func__.2837
0000000000000098 r __func__.2842
U _GLOBAL_OFFSET_TABLE_
U perror
U printf
0000000000000000 T regget
00000000000000e3 T regset
U __stack_chk_fail
```
:::spoiler
ar --h
Usage: ar [emulation options] [-]{dmpqrstx}[abcDfilMNoOPsSTuvV] [--plugin <name>] [member-name] [count] archive-file file...
ar -M [<mri-script]
commands:
d - delete file(s) from the archive
m[ab] - move file(s) in the archive
p - print file(s) found in the archive
q[f] - quick append file(s) to the archive
r[ab][f][u] - replace existing or insert new file(s) into the archive
s - act as ranlib
t[O][v] - display contents of the archive
x[o] - extract file(s) from the archive
command specific modifiers:
[a] - put file(s) after [member-name]
[b] - put file(s) before [member-name] (same as [i])
[D] - use zero for timestamps and uids/gids (default)
[U] - use actual timestamps and uids/gids
[N] - use instance [count] of name
[f] - truncate inserted file names
[P] - use full path names when matching
[o] - preserve original dates
[O] - display offsets of files in the archive
[u] - only replace files that are newer than current archive contents
generic modifiers:
[c] - do not warn if the library had to be created
[s] - create an archive index (cf. ranlib)
[S] - do not build a symbol table
[T] - make a thin archive
[v] - be verbose
[V] - display the version number
@<file> - read options from <file>
--target=BFDNAME - specify the target object format as BFDNAME
--output=DIRNAME - specify the output directory for extraction operations
optional:
--plugin <p> - load the specified plugin
emulation options:
No emulation specific options
ar: supported targets: elf64-x86-64 elf32-i386 elf32-iamcu elf32-x86-64 pei-i386 pei-x86-64 elf64-l1om elf64-k1om elf64-little elf64-big elf32-little elf32-big pe-x86-64 pe-bigobj-x86-64 pe-i386 srec symbolsrec verilog tekhex binary ihex plugin
Report bugs to <http://www.sourceware.org/bugzilla/>
:::
### Build the application and link it with a static library
1. Compile the application as hello and link it with libregapi.a
```shell
Tomas# gcc main.c libregapi.a -o hello -Iregapi/include
Tomas# ls -al hello
-rwxrwxr-x 1 tomas tomas 17208 十 22 20:06 hello
-rw-rw-r-- 1 tomas tomas 3242 十 22 19:55 libregapi.a
-rw-rw-r-- 1 tomas tomas 741 十 22 19:35 main.c
drwxrwxr-x 4 tomas tomas 4096 十 22 17:25 regapi
-rw-rw-r-- 1 tomas tomas 3088 十 22 19:53 regapi.o
-rw-rw-r-- 1 tomas tomas 1 十 22 20:07 reg.txt
```
2. Execute it
```shell
Tomas# ./hello
Usage: ./hello [get | set <value>]
Tomas#./hello set 5
set reg value to 5
Call regset to set reg value 5
Tomas# ./hello get
Call regget to get reg value 5
get reg value: 5
```
3. Check symbols by nm
```bash
Tomas# nm hello
0000000000003d80 d __do_global_dtors_aux_fini_array_entry
0000000000004008 D __dso_handle
0000000000003d88 d _DYNAMIC
0000000000004010 D _edata
0000000000004018 B _end
U fclose@@GLIBC_2.2.5
U fgets@@GLIBC_2.2.5
0000000000001548 T _fini
U fopen@@GLIBC_2.2.5
U fprintf@@GLIBC_2.2.5
0000000000001240 t frame_dummy
0000000000003d78 d __frame_dummy_init_array_entry
00000000000022dc r __FRAME_END__
0000000000002131 r __func__.2837
0000000000002138 r __func__.2842
0000000000003f78 d _GLOBAL_OFFSET_TABLE_
w __gmon_start__
0000000000002140 r __GNU_EH_FRAME_HDR
0000000000001000 t _init
0000000000003d80 d __init_array_end
0000000000003d78 d __init_array_start
0000000000002000 R _IO_stdin_used
w _ITM_deregisterTMCloneTable
w _ITM_registerTMCloneTable
0000000000001540 T __libc_csu_fini
00000000000014d0 T __libc_csu_init
U __libc_start_main@@GLIBC_2.2.5
0000000000001249 T main
U perror@@GLIBC_2.2.5
U printf@@GLIBC_2.2.5
000000000000136e T regget
00000000000011c0 t register_tm_clones
0000000000001451 T regset
U __stack_chk_fail@@GLIBC_2.4
0000000000001160 T _start
U strcmp@@GLIBC_2.2.5
0000000000004010 D __TMC_END__
```
:::spoiler
```shell
Tomas# readelf -a libregapi.a
File: libregapi.a(regapi.o)
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: REL (Relocatable file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x0
Start of program headers: 0 (bytes into file)
Start of section headers: 2192 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 0 (bytes)
Number of program headers: 0
Size of section headers: 64 (bytes)
Number of section headers: 14
Section header string table index: 13
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .text PROGBITS 0000000000000000 00000040
0000000000000158 0000000000000000 AX 0 0 1
[ 2] .rela.text RELA 0000000000000000 00000590
0000000000000258 0000000000000018 I 11 1 8
[ 3] .data PROGBITS 0000000000000000 00000198
0000000000000000 0000000000000000 WA 0 0 1
[ 4] .bss NOBITS 0000000000000000 00000198
0000000000000000 0000000000000000 WA 0 0 1
[ 5] .rodata PROGBITS 0000000000000000 00000198
[ 8] .note.gnu.propert NOTE 0000000000000000 00000268
0000000000000020 0000000000000000 A 0 0 8
[ 9] .eh_frame PROGBITS 0000000000000000 00000288
0000000000000058 0000000000000000 A 0 0 8
[10] .rela.eh_frame RELA 0000000000000000 000007e8
0000000000000030 0000000000000018 I 11 9 8
[11] .symtab SYMTAB 0000000000000000 000002e0
0000000000000228 0000000000000018 12 12 8
[12] .strtab STRTAB 0000000000000000 00000508
0000000000000082 0000000000000000 0 0 1
[13] .shstrtab STRTAB 0000000000000000 00000818
0000000000000074 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
l (large), p (processor specific)
There are no section groups in this file.
There are no program headers in this file.
There is no dynamic section in this file.
Relocation section '.rela.text' at offset 0x590 contains 25 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000000021 000500000002 R_X86_64_PC32 0000000000000000 .rodata - 4
000000000028 000500000002 R_X86_64_PC32 0000000000000000 .rodata - 2
00000000002d 000e00000004 R_X86_64_PLT32 0000000000000000 fopen - 4
000000000045 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 6
00000000004a 000f00000004 R_X86_64_PLT32 0000000000000000 perror - 4
000000000051 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 8d
000000000058 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 24
000000000062 001000000004 R_X86_64_PLT32 0000000000000000 printf - 4
000000000084 001100000004 R_X86_64_PLT32 0000000000000000 fgets - 4
00000000009a 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 8d
0000000000a1 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 4e
0000000000ab 001000000004 R_X86_64_PLT32 0000000000000000 printf - 4
0000000000ba 001200000004 R_X86_64_PLT32 0000000000000000 fclose - 4
0000000000c9 001300000004 R_X86_64_PLT32 0000000000000000 atoi - 4
0000000000dd 001400000004 R_X86_64_PLT32 0000000000000000 __stack_chk_fail - 4
0000000000f5 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 6b
0000000000fc 000500000002 R_X86_64_PC32 0000000000000000 .rodata - 2
000000000101 000e00000004 R_X86_64_PLT32 0000000000000000 fopen - 4
000000000113 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 6
000000000118 000f00000004 R_X86_64_PLT32 0000000000000000 perror - 4
000000000126 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 94
00000000012d 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 6d
000000000137 001000000004 R_X86_64_PLT32 0000000000000000 printf - 4
000000000145 000500000002 R_X86_64_PC32 0000000000000000 .rodata + 8a
000000000152 001600000004 R_X86_64_PLT32 0000000000000000 fprintf - 4
Relocation section '.rela.eh_frame' at offset 0x7e8 contains 2 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000000020 000200000002 R_X86_64_PC32 0000000000000000 .text + 0
000000000040 000200000002 R_X86_64_PC32 0000000000000000 .text + e3
The decoding of unwind sections for machine type Advanced Micro Devices X86-64 is not currently supported.
Symbol table '.symtab' contains 23 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 FILE LOCAL DEFAULT ABS regapi.c
2: 0000000000000000 0 SECTION LOCAL DEFAULT 1
3: 0000000000000000 0 SECTION LOCAL DEFAULT 3
4: 0000000000000000 0 SECTION LOCAL DEFAULT 4
5: 0000000000000000 0 SECTION LOCAL DEFAULT 5
6: 0000000000000091 7 OBJECT LOCAL DEFAULT 5 __func__.2837
7: 0000000000000098 7 OBJECT LOCAL DEFAULT 5 __func__.2842
8: 0000000000000000 0 SECTION LOCAL DEFAULT 7
9: 0000000000000000 0 SECTION LOCAL DEFAULT 8
10: 0000000000000000 0 SECTION LOCAL DEFAULT 9
11: 0000000000000000 0 SECTION LOCAL DEFAULT 6
12: 0000000000000000 227 FUNC GLOBAL DEFAULT 1 regget
13: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND _GLOBAL_OFFSET_TABLE_
14: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND fopen
15: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND perror
16: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND printf
17: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND fgets
18: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND fclose
19: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND atoi
20: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND __stack_chk_fail
21: 00000000000000e3 117 FUNC GLOBAL DEFAULT 1 regset
22: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND fprintf
No version information found in this file.
Displaying notes found in: .note.gnu.property
Owner Data size Description
GNU 0x00000010 NT_GNU_PROPERTY_TYPE_0
Properties: x86 feature: IBT, SHSTK
:::
:::spoiler
Tomas# readelf -a hello
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: DYN (Shared object file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x1160
Start of program headers: 64 (bytes into file)
Start of section headers: 15224 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 13
Size of section headers: 64 (bytes)
Number of section headers: 31
Section header string table index: 30
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .interp PROGBITS 0000000000000318 00000318
000000000000001c 0000000000000000 A 0 0 1
[ 2] .note.gnu.propert NOTE 0000000000000338 00000338
0000000000000020 0000000000000000 A 0 0 8
[ 3] .note.gnu.build-i NOTE 0000000000000358 00000358
0000000000000024 0000000000000000 A 0 0 4
000000000000000d 0000000000000000 AX 0 0 4
[18] .rodata PROGBITS 0000000000002000 00002000
000000000000013f 0000000000000000 A 0 0 8
[19] .eh_frame_hdr PROGBITS 0000000000002140 00002140
0000000000000054 0000000000000000 A 0 0 4
[20] .eh_frame PROGBITS 0000000000002198 00002198
0000000000000148 0000000000000000 A 0 0 8
[21] .init_array INIT_ARRAY 0000000000003d78 00002d78
0000000000000008 0000000000000008 WA 0 0 8
[22] .fini_array FINI_ARRAY 0000000000003d80 00002d80
0000000000000008 0000000000000008 WA 0 0 8
[23] .dynamic DYNAMIC 0000000000003d88 00002d88
00000000000001f0 0000000000000010 WA 7 0 8
[24] .got PROGBITS 0000000000003f78 00002f78
0000000000000088 0000000000000008 WA 0 0 8
[25] .data PROGBITS 0000000000004000 00003000
0000000000000010 0000000000000000 WA 0 0 8
[26] .bss NOBITS 0000000000004010 00003010
0000000000000008 0000000000000000 WA 0 0 1
[27] .comment PROGBITS 0000000000000000 00003010
000000000000002b 0000000000000001 MS 0 0 1
[28] .symtab SYMTAB 0000000000000000 00003040
0000000000000750 0000000000000018 29 49 8
[29] .strtab STRTAB 0000000000000000 00003790
00000000000002c8 0000000000000000 0 0 1
[30] .shstrtab STRTAB 0000000000000000 00003a58
000000000000011a 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
l (large), p (processor specific)
There are no section groups in this file.
Program Headers:
Type Offset VirtAddr PhysAddr
on_r .rela.dyn .rela.plt
03 .init .plt .plt.got .plt.sec .text .fini
04 .rodata .eh_frame_hdr .eh_frame
05 .init_array .fini_array .dynamic .got .data .bss
06 .dynamic
07 .note.gnu.property
08 .note.gnu.build-id .note.ABI-tag
09 .note.gnu.property
10 .eh_frame_hdr
11
12 .init_array .fini_array .dynamic .got
Dynamic section at offset 0x2d88 contains 27 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000c (INIT) 0x1000
0x000000000000000d (FINI) 0x1548
0x0000000000000019 (INIT_ARRAY) 0x3d78
0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
0x000000000000001a (FINI_ARRAY) 0x3d80
0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x3a0
0x0000000000000005 (STRTAB) 0x530
0x0000000000000006 (SYMTAB) 0x3c8
0x000000000000000a (STRSZ) 198 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000015 (DEBUG) 0x0
0x0000000000000003 (PLTGOT) 0x3f78
0x0000000000000002 (PLTRELSZ) 216 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x708
0x0000000000000007 (RELA) 0x648
0x0000000000000008 (RELASZ) 192 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x000000000000001e (FLAGS) BIND_NOW
0x000000006ffffffb (FLAGS_1) Flags: NOW PIE
0x000000006ffffffe (VERNEED) 0x618
Relocation section '.rela.dyn' at offset 0x648 contains 8 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000003d78 000000000008 R_X86_64_RELATIVE 1240
000000003d80 000000000008 R_X86_64_RELATIVE 1200
000000004008 000000000008 R_X86_64_RELATIVE 4008
000000003fd8 000100000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_deregisterTMClone + 0
000000003fe0 000500000006 R_X86_64_GLOB_DAT 0000000000000000 __libc_start_main@GLIBC_2.2.5 + 0
000000003fe8 000900000006 R_X86_64_GLOB_DAT 0000000000000000 __gmon_start__ + 0
000000003ff0 000d00000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_registerTMCloneTa + 0
000000003ff8 000e00000006 R_X86_64_GLOB_DAT 0000000000000000 __cxa_finalize@GLIBC_2.2.5 + 0
Relocation section '.rela.plt' at offset 0x708 contains 9 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000003f90 000200000007 R_X86_64_JUMP_SLO 0000000000000000 fclose@GLIBC_2.2.5 + 0
000000003f98 000300000007 R_X86_64_JUMP_SLO 0000000000000000 __stack_chk_fail@GLIBC_2.4 + 0
000000003fa0 000400000007 R_X86_64_JUMP_SLO 0000000000000000 printf@GLIBC_2.2.5 + 0
000000003fa8 000600000007 R_X86_64_JUMP_SLO 0000000000000000 fgets@GLIBC_2.2.5 + 0
000000003fb0 000700000007 R_X86_64_JUMP_SLO 0000000000000000 strcmp@GLIBC_2.2.5 + 0
000000003fb8 000800000007 R_X86_64_JUMP_SLO 0000000000000000 fprintf@GLIBC_2.2.5 + 0
000000003fc0 000a00000007 R_X86_64_JUMP_SLO 0000000000000000 fopen@GLIBC_2.2.5 + 0
000000003fc8 000b00000007 R_X86_64_JUMP_SLO 0000000000000000 perror@GLIBC_2.2.5 + 0
000000003fd0 000c00000007 R_X86_64_JUMP_SLO 0000000000000000 atoi@GLIBC_2.2.5 + 0
The decoding of unwind sections for machine type Advanced Micro Devices X86-64 is not currently supported.
Symbol table '.dynsym' contains 15 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTab
2: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fclose@GLIBC_2.2.5 (2)
3: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __stack_chk_fail@GLIBC_2.4 (3)
4: 0000000000000000 0 FUNC GLOBAL DEFAULT UND printf@GLIBC_2.2.5 (2)
5: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.2.5 (2)
6: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fgets@GLIBC_2.2.5 (2)
7: 0000000000000000 0 FUNC GLOBAL DEFAULT UND strcmp@GLIBC_2.2.5 (2)
8: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fprintf@GLIBC_2.2.5 (2)
9: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
4: 000000000000037c 0 SECTION LOCAL DEFAULT 4
5: 00000000000003a0 0 SECTION LOCAL DEFAULT 5
6: 00000000000003c8 0 SECTION LOCAL DEFAULT 6
7: 0000000000000530 0 SECTION LOCAL DEFAULT 7
8: 00000000000005f6 0 SECTION LOCAL DEFAULT 8
9: 0000000000000618 0 SECTION LOCAL DEFAULT 9
10: 0000000000000648 0 SECTION LOCAL DEFAULT 10
11: 0000000000000708 0 SECTION LOCAL DEFAULT 11
12: 0000000000001000 0 SECTION LOCAL DEFAULT 12
13: 0000000000001020 0 SECTION LOCAL DEFAULT 13
14: 00000000000010c0 0 SECTION LOCAL DEFAULT 14
15: 00000000000010d0 0 SECTION LOCAL DEFAULT 15
16: 0000000000001160 0 SECTION LOCAL DEFAULT 16
17: 0000000000001548 0 SECTION LOCAL DEFAULT 17
18: 0000000000002000 0 SECTION LOCAL DEFAULT 18
19: 0000000000002140 0 SECTION LOCAL DEFAULT 19
20: 0000000000002198 0 SECTION LOCAL DEFAULT 20
21: 0000000000003d78 0 SECTION LOCAL DEFAULT 21
22: 0000000000003d80 0 SECTION LOCAL DEFAULT 22
23: 0000000000003d88 0 SECTION LOCAL DEFAULT 23
24: 0000000000003f78 0 SECTION LOCAL DEFAULT 24
25: 0000000000004000 0 SECTION LOCAL DEFAULT 25
26: 0000000000004010 0 SECTION LOCAL DEFAULT 26
27: 0000000000000000 0 SECTION LOCAL DEFAULT 27
28: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
29: 0000000000001190 0 FUNC LOCAL DEFAULT 16 deregister_tm_clones
30: 00000000000011c0 0 FUNC LOCAL DEFAULT 16 register_tm_clones
31: 0000000000001200 0 FUNC LOCAL DEFAULT 16 __do_global_dtors_aux
32: 0000000000004010 1 OBJECT LOCAL DEFAULT 26 completed.8061
33: 0000000000003d80 0 OBJECT LOCAL DEFAULT 22 __do_global_dtors_aux_fin
34: 0000000000001240 0 FUNC LOCAL DEFAULT 16 frame_dummy
35: 0000000000003d78 0 OBJECT LOCAL DEFAULT 21 __frame_dummy_init_array_
36: 0000000000000000 0 FILE LOCAL DEFAULT ABS main.c
37: 0000000000000000 0 FILE LOCAL DEFAULT ABS regapi.c
38: 0000000000002131 7 OBJECT LOCAL DEFAULT 18 __func__.2837
39: 0000000000002138 7 OBJECT LOCAL DEFAULT 18 __func__.2842
40: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
54: 0000000000001548 0 FUNC GLOBAL HIDDEN 17 _fini
55: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __stack_chk_fail@@GLIBC_2
56: 0000000000000000 0 FUNC GLOBAL DEFAULT UND printf@@GLIBC_2.2.5
57: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@@GLIBC_
58: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fgets@@GLIBC_2.2.5
59: 0000000000004000 0 NOTYPE GLOBAL DEFAULT 25 __data_start
60: 0000000000000000 0 FUNC GLOBAL DEFAULT UND strcmp@@GLIBC_2.2.5
61: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fprintf@@GLIBC_2.2.5
62: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
63: 0000000000004008 0 OBJECT GLOBAL HIDDEN 25 __dso_handle
64: 0000000000002000 4 OBJECT GLOBAL DEFAULT 18 _IO_stdin_used
65: 00000000000014d0 101 FUNC GLOBAL DEFAULT 16 __libc_csu_init
66: 0000000000004018 0 NOTYPE GLOBAL DEFAULT 26 _end
67: 0000000000001160 47 FUNC GLOBAL DEFAULT 16 _start
68: 0000000000004010 0 NOTYPE GLOBAL DEFAULT 26 __bss_start
69: 0000000000001249 293 FUNC GLOBAL DEFAULT 16 main
70: 0000000000001451 117 FUNC GLOBAL DEFAULT 16 regset
71: 000000000000136e 227 FUNC GLOBAL DEFAULT 16 regget
72: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fopen@@GLIBC_2.2.5
73: 0000000000000000 0 FUNC GLOBAL DEFAULT UND perror@@GLIBC_2.2.5
74: 0000000000000000 0 FUNC GLOBAL DEFAULT UND atoi@@GLIBC_2.2.5
75: 0000000000004010 0 OBJECT GLOBAL HIDDEN 25 __TMC_END__
76: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMCloneTable
77: 0000000000000000 0 FUNC WEAK DEFAULT UND __cxa_finalize@@GLIBC_2.2
Histogram for `.gnu.hash' bucket list length (total of 2 buckets):
Length Number % of total Coverage
0 1 ( 50.0%)
1 1 ( 50.0%) 100.0%
Version symbols section '.gnu.version' contains 15 entries:
Addr: 0x00000000000005f6 Offset: 0x0005f6 Link: 6 (.dynsym)
000: 0 (*local*) 0 (*local*) 2 (GLIBC_2.2.5) 3 (GLIBC_2.4)
004: 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5)
008: 2 (GLIBC_2.2.5) 0 (*local*) 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5)
00c: 2 (GLIBC_2.2.5) 0 (*local*) 2 (GLIBC_2.2.5)
Version needs section '.gnu.version_r' contains 1 entry:
Addr: 0x0000000000000618 Offset: 0x000618 Link: 7 (.dynstr)
000000: Version: 1 File: libc.so.6 Cnt: 2
0x0010: Name: GLIBC_2.4 Flags: none Version: 3
0x0020: Name: GLIBC_2.2.5 Flags: none Version: 2
Displaying notes found in: .note.gnu.property
Owner Data size Description
GNU 0x00000010 NT_GNU_PROPERTY_TYPE_0
Properties: x86 feature: IBT, SHSTK
Displaying notes found in: .note.gnu.build-id
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring)
Build ID: 353ed780fae95a5ba1e16889cafbc321fe205f40
Displaying notes found in: .note.ABI-tag
Owner Data size Description
GNU 0x00000010 NT_GNU_ABI_TAG (ABI version tag)
OS: Linux, ABI: 3.2.0
:::
### Write the Makefile and build it
```shell
Tomas # ls -al
-rw-rw-r-- 1 tomas tomas 741 十 22 19:35 main.c
-rw-rw-r-- 1 tomas tomas 603 十 22 20:44 Makefile
drwxrwxr-x 4 tomas tomas 4096 十 22 17:25 regapi
Tomas# cat Makefile
# Compiler and flags
CC = gcc
CFLAGS = -Wall -Wextra -Iregapi/include
LDFLAGS = -L. -lregapi
# Source files and objects
SRC = main.c
LIB_SRC = regapi/src/regapi.c
OBJ = $(SRC:.c=.o) regapi.o
# Target executable
TARGET = hello
.PHONY: all clean
all: $(TARGET)
# Build the static library
libregapi.a: regapi.o
ar rcs $@ $^
# Compile the library source file
regapi.o: $(LIB_SRC)
$(CC) $(CFLAGS) -c $<
# Build the main executable
$(TARGET): $(OBJ) libregapi.a
$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
# Compile source files
%.o: %.c
$(CC) $(CFLAGS) -c $<
clean:
rm -f $(TARGET) $(OBJ) libregapi.a
```
---
## Dynamic library
1. Compile the regapi.c to an object by gcc.
```shell
Tomas# gcc -fPIC -c regapi/src/regapi.c -Iregapi/include
Tomas# ls -al regapi.o
-rw-rw-r-- 1 tomas tomas 3088 十 22 20:48 regapi.o
```
2. Create the shared library
```shell
Tomas# gcc -s -shared -o libregapi.so regapi.o
Tomas# ls -al
-rwxrwxr-x 1 tomas tomas 14472 十 22 20:49 libregapi.so
-rw-rw-r-- 1 tomas tomas 741 十 22 19:35 main.c
-rw-rw-r-- 1 tomas tomas 603 十 22 20:44 Makefile
drwxrwxr-x 4 tomas tomas 4096 十 22 17:25 regapi
-rw-rw-r-- 1 tomas tomas 3088 十 22 20:48 regapi.o
```
3. Check the library dependency by ldd
```shell
Tomas# ldd libregapi.so
linux-vdso.so.1 (0x00007ffd05254000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f4652994000)
/lib64/ld-linux-x86-64.so.2 (0x00007f4652b9f000)
```
### Build the application and link it with shared library
```
Tomas# gcc -o hello main.c -Wl,-rpath=. -L. -Iregapi/include -lregapi
Tomas# ls -al
-rwxrwxr-x 1 tomas tomas 16848 十 22 20:56 hello
-rwxrwxr-x 1 tomas tomas 14472 十 22 20:53 libregapi.so
-rw-rw-r-- 1 tomas tomas 741 十 22 19:35 main.c
-rw-rw-r-- 1 tomas tomas 603 十 22 20:44 Makefile
drwxrwxr-x 4 tomas tomas 4096 十 22 17:25 regapi
```
Execute it.
```shell
Tomas# ./hello set 88
set reg value to 88
Call regset to set reg value 88
Tomas# ./hello get
Call regget to get reg value 88
reg value: 88
```
Check the symbols.
```
Tomas# nm hello
U atoi@@GLIBC_2.2.5
0000000000004010 B __bss_start
0000000000004010 b completed.8061
w __cxa_finalize@@GLIBC_2.2.5
0000000000004000 D __data_start
0000000000004000 W data_start
0000000000001110 t deregister_tm_clones
0000000000001180 t __do_global_dtors_aux
0000000000003d80 d __do_global_dtors_aux_fini_array_entry
0000000000004008 D __dso_handle
0000000000003d88 d _DYNAMIC
0000000000004010 D _edata
0000000000004018 B _end
0000000000001368 T _fini
00000000000011c0 t frame_dummy
0000000000003d78 d __frame_dummy_init_array_entry
00000000000021ec r __FRAME_END__
0000000000003f98 d _GLOBAL_OFFSET_TABLE_
w __gmon_start__
00000000000020a0 r __GNU_EH_FRAME_HDR
0000000000001000 t _init
0000000000003d80 d __init_array_end
0000000000003d78 d __init_array_start
0000000000002000 R _IO_stdin_used
w _ITM_deregisterTMCloneTable
w _ITM_registerTMCloneTable
0000000000001360 T __libc_csu_fini
00000000000012f0 T __libc_csu_init
U __libc_start_main@@GLIBC_2.2.5
00000000000011c9 T main
U printf@@GLIBC_2.2.5
U regget
0000000000001140 t register_tm_clones
U regset
00000000000010e0 T _start
U strcmp@@GLIBC_2.2.5
0000000000004010 D __TMC_END__
```
:::spoiler
```shell
Tomas# readelf -a libregapi.so
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: DYN (Shared object file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x1140
Start of program headers: 64 (bytes into file)
Start of section headers: 12680 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 11
Size of section headers: 64 (bytes)
Number of section headers: 28
Section header string table index: 27
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .note.gnu.propert NOTE 00000000000002a8 000002a8
0000000000000020 0000000000000000 A 0 0 8
[ 2] .note.gnu.build-i NOTE 00000000000002c8 000002c8
0000000000000024 0000000000000000 A 0 0 4
[ 3] .gnu.hash GNU_HASH 00000000000002f0 000002f0
0000000000000028 0000000000000000 A 4 0 8
[15] .fini PROGBITS 0000000000001354 00001354
000000000000000d 0000000000000000 AX 0 0 4
[16] .rodata PROGBITS 0000000000002000 00002000
000000000000009f 0000000000000000 A 0 0 8
[17] .eh_frame_hdr PROGBITS 00000000000020a0 000020a0
0000000000000034 0000000000000000 A 0 0 4
[18] .eh_frame PROGBITS 00000000000020d8 000020d8
00000000000000b4 0000000000000000 A 0 0 8
[19] .init_array INIT_ARRAY 0000000000003e10 00002e10
0000000000000008 0000000000000008 WA 0 0 8
[20] .fini_array FINI_ARRAY 0000000000003e18 00002e18
0000000000000008 0000000000000008 WA 0 0 8
[21] .dynamic DYNAMIC 0000000000003e20 00002e20
00000000000001c0 0000000000000010 WA 5 0 8
[22] .got PROGBITS 0000000000003fe0 00002fe0
0000000000000020 0000000000000008 WA 0 0 8
[23] .got.plt PROGBITS 0000000000004000 00003000
0000000000000058 0000000000000008 WA 0 0 8
[24] .data PROGBITS 0000000000004058 00003058
0000000000000008 0000000000000000 WA 0 0 8
[25] .bss NOBITS 0000000000004060 00003060
0000000000000008 0000000000000000 WA 0 0 1
[26] .comment PROGBITS 0000000000000000 00003060
000000000000002b 0000000000000001 MS 0 0 1
[27] .shstrtab STRTAB 0000000000000000 0000308b
00000000000000fd 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
l (large), p (processor specific)
There are no section groups in this file.
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x00000000000006f8 0x00000000000006f8 R 0x1000
LOAD 0x0000000000001000 0x0000000000001000 0x0000000000001000
0x0000000000000361 0x0000000000000361 R E 0x1000
LOAD 0x0000000000002000 0x00000000000020
Dynamic section at offset 0x2e20 contains 24 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000c (INIT) 0x1000
0x000000000000000d (FINI) 0x1354
0x0000000000000019 (INIT_ARRAY) 0x3e10
0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
0x000000000000001a (FINI_ARRAY) 0x3e18
0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x2f0
0x0000000000000005 (STRTAB) 0x480
0x0000000000000006 (SYMTAB) 0x318
0x000000000000000a (STRSZ) 187 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000003 (PLTGOT) 0x4000
0x0000000000000002 (PLTRELSZ) 192 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x638
0x0000000000000007 (RELA) 0x590
0x0000000000000008 (RELASZ) 168 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x000000006ffffffe (VERNEED) 0x560
0x000000006fffffff (VERNEEDNUM) 1
0x000000006ffffff0 (VERSYM) 0x53c
0x000000006ffffff9 (RELACOUNT) 3
0x0000000000000000 (NULL) 0x0
Relocation section '.rela.dyn' at offset 0x590 contains 7 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000003e10 000000000008 R_X86_64_RELATIVE 11f0
000000003e18 000000000008 R_X86_64_RELATIVE 11b0
000000004058 000000000008 R_X86_64_RELATIVE 4058
000000003fe0 000100000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_deregisterTMClone + 0
000000003fe8 000700000006 R_X86_64_GLOB_DAT 0000000000000000 __gmon_start__ + 0
000000003ff0 000b00000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_registerTMCloneTa + 0
000000003ff8 000c00000006 R_X86_64_GLOB_DAT 0000000000000000 __cxa_finalize@GLIBC_2.2.5 + 0
Relocation section '.rela.plt' at offset 0x638 contains 8 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000004018 000200000007 R_X86_64_JUMP_SLO 0000000000000000 fclose@GLIBC_2.2.5 + 0
000000004020 000300000007 R_X86_6
The decoding of unwind sections for machine type Advanced Micro Devices X86-64 is not currently supported.
Symbol table '.dynsym' contains 15 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTab
2: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fclose@GLIBC_2.2.5 (2)
3: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __stack_chk_fail@GLIBC_2.4 (3)
4: 0000000000000000 0 FUNC GLOBAL DEFAULT UND printf@GLIBC_2.2.5 (2)
5: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fgets@GLIBC_2.2.5 (2)
6: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fprintf@GLIBC_2.2.5 (2)
7: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
8: 0000000000000000 0 FUNC GLOBAL DEFAULT UND fopen@GLIBC_2.2.5 (2)
9: 0000000000000000 0 FUNC GLOBAL DEFAULT UND perror@GLIBC_2.2.5 (2)
10: 0000000000000000 0 FUNC GLOBAL DEFAULT UND atoi@GLIBC_2.2.5 (2)
11: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMCloneTable
12: 0000000000000000 0 FUNC WEAK DEFAULT UND __cxa_finalize@GLIBC_2.2.5 (2)
13: 00000000000012dc 117 FUNC GLOBAL DEFAULT 14 regset
14: 00000000000011f9 227 FUNC GLOBAL DEFAULT 14 regget
Histogram for `.gnu.hash' bucket list length (total of 2 buckets):
Length Number % of total Coverage
0 1 ( 50.0%)
1 0 ( 0.0%) 0.0%
2 1 ( 50.0%) 100.0%
Version symbols section '.gnu.version' contains 15 entries:
Addr: 0x000000000000053c Offset: 0x00053c Link: 4 (.dynsym)
000: 0 (*local*) 0 (*local*) 2 (GLIBC_2.2.5) 3 (GLIBC_2.4)
004: 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5) 0 (*local*)
008: 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5) 0 (*local*)
00c: 2 (GLIBC_2.2.5) 1 (*global*) 1 (*global*)
Version needs section '.gnu.version_r' contains 1 entry:
Addr: 0x0000000000000560 Offset: 0x000560 Link: 5 (.dynstr)
000000: Version: 1 File: libc.so.6 Cnt: 2
0x0010: Name: GLIBC_2.4 Flags: none Version: 3
0x0020: Name: GLIBC_2.2.5 Flags: none Version: 2
Displaying notes found in: .note.gnu.property
Owner Data size Description
GNU 0x00000010 NT_GNU_PROPERTY_TYPE_0
Properties: x86 feature: IBT, SHSTK
Displaying notes found in: .note.gnu.build-id
Owner Data size Description
GNU 0x00000014 NT_GNU_BUILD_ID (unique build ID bitstring)
Build ID: c172a62c7d23fe26fa3127ba7d4ceaeb6fce920e
```
:::
:::spoiler
Tomas# readelf -a hello
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: DYN (Shared object file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x10e0
Start of program headers: 64 (bytes into file)
Start of section headers: 14864 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 13
Size of section headers: 64 (bytes)
Number of section headers: 31
Section header string table index: 30
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .interp PROGBITS 0000000000000318 00000318
0000000000000016 0000000000000002 A 6 0 2
[ 9] .gnu.version_r VERNEED 0000000000000598 00000598
0000000000000020 0000000000000000 A 7 1 8
[10] .rela.dyn RELA 00000000000005b8 000005b8
00000000000000c0 0000000000000018 A 6 0 8
[11] .rela.plt RELA 0000000000000678 00000678
0000000000000078 0000000000000018 AI 6 24 8
[12] .init PROGBITS 0000000000001000 00001000
000000000000001b 0000000000000000 AX 0 0 4
[13] .plt PROGBITS 0000000000001020 00001020
0000000000000060 0000000000000010 AX 0 0 16
[14] .plt.got PROGBITS 0000000000001080 00001080
0000000000000010 0000000000000010 AX 0 0 16
[15] .plt.sec PROGBITS 0000000000001090 00001090
0000000000000050 0000000000000010 AX 0 0 16
[16] .text PROGBITS 00000000000010e0 000010e0
0000000000000285 0000000000000000 AX 0 0 16
[17] .fini PROGBITS 0000000000001368 00001368
000000000000000d 0000000000000000 AX 0 0 4
[18] .rodata PROGBITS 0000000000002000 00002000
00000000000000a0 0000000000000000 A 0 0 8
[19] .eh_frame_hdr PROGBITS 00000000000020a0 000020a0
0000000000000044 0000000000000000 A 0 0 4
[20] .eh_frame PROGBITS 00000000000020e8 000020e8
0000000000000108 0000000000000000 A 0 0 8
[21] .init_array INIT_ARRAY 0000000000003d78 00002d78
0000000000000008 0000000000000008 WA 0 0 8
[22] .fini_array FINI_ARRAY 0000000000003d80 00002d80
0000000000000008 0000000000000008 WA 0 0 8
[23] .dynamic DYNAMIC 0000000000003d88 00002d88
0000000000000210 0000000000000010 WA 7 0 8
[24] .got PROGBITS 0000000000003f98 00002f98
0000000000000068 0000000000000008 WA 0 0 8
[25] .data PROGBITS 0000000000004000 00003000
0000000000000010 0000000000000000 WA 0 0 8
[26] .bss NOBITS 0000000000004010 00003010
0000000000000008 0000000000000000 WA 0 0 1
[27] .comment PROGBITS 0000000000000000 00003010
000000000000002b 0000000000000001 MS 0 0 1
[28] .symtab SYMTAB 0000000000000000 00003040
0000000000000678 0000000000000018 29 46 8
0x0000000000000044 0x0000000000000044 R 0x4
GNU_PROPERTY 0x0000000000000338 0x0000000000000338 0x0000000000000338
0x0000000000000020 0x0000000000000020 R 0x8
GNU_EH_FRAME 0x00000000000020a0 0x00000000000020a0 0x00000000000020a0
0x0000000000000044 0x0000000000000044 R 0x4
GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 RW 0x10
GNU_RELRO 0x0000000000002d78 0x0000000000003d78 0x0000000000003d78
0x0000000000000288 0x0000000000000288 R 0x1
Section to Segment mapping:
Segment Sections...
00
01 .interp
02 .interp .note.gnu.property .note.gnu.build-id .note.ABI-tag .gnu.hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn .rela.plt
03 .init .plt .plt.got .plt.sec .text .fini
04 .rodata .eh_frame_hdr .eh_frame
05 .init_array .fini_array .dynamic .got .data .bss
06 .dynamic
07 .note.gnu.property
08 .note.gnu.build-id .note.ABI-tag
09 .note.gnu.property
10 .eh_frame_hdr
11
12 .init_array .fini_array .dynamic .got
Dynamic section at offset 0x2d88 contains 29 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libregapi.so]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000001d (RUNPATH) Library runpath: [.]
0x000000000000000c (INIT) 0x1000
0x000000000000000d (FINI) 0x1368
0x0000000000000019 (INIT_ARRAY) 0x3d78
0x000000000000001b (INIT_ARRAYSZ) 8 (bytes)
0x000000000000001a (FINI_ARRAY) 0x3d80
0x000000000000001c (FINI_ARRAYSZ) 8 (bytes)
0x000000006ffffef5 (GNU_HASH) 0x3a0
0x0000000000000005 (STRTAB) 0x4d0
0x0000000000000006 (SYMTAB) 0x3c8
0x000000000000000a (STRSZ) 173 (bytes)
0x000000006ffffff0 (VERSYM) 0x57e
0x000000006ffffff9 (RELACOUNT) 3
0x0000000000000000 (NULL) 0x0
Relocation section '.rela.dyn' at offset 0x5b8 contains 8 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000003d78 000000000008 R_X86_64_RELATIVE 11c0
000000003d80 000000000008 R_X86_64_RELATIVE 1180
000000004008 000000000008 R_X86_64_RELATIVE 4008
000000003fd8 000100000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_deregisterTMClone + 0
000000003fe0 000300000006 R_X86_64_GLOB_DAT 0000000000000000 __libc_start_main@GLIBC_2.2.5 + 0
000000003fe8 000500000006 R_X86_64_GLOB_DAT 0000000000000000 __gmon_start__ + 0
000000003ff0 000900000006 R_X86_64_GLOB_DAT 0000000000000000 _ITM_registerTMCloneTa + 0
000000003ff8 000a00000006 R_X86_64_GLOB_DAT 0000000000000000 __cxa_finalize@GLIBC_2.2.5 + 0
Relocation section '.rela.plt' at offset 0x678 contains 5 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000003fb0 000200000007 R_X86_64_JUMP_SLO 0000000000000000 printf@GLIBC_2.2.5 + 0
000000003fb8 000400000007 R_X86_64_JUMP_SLO 0000000000000000 strcmp@GLIBC_2.2.5 + 0
000000003fc0 000600000007 R_X86_64_JUMP_SLO 0000000000000000 regset + 0
000000003fc8 000700000007 R_X86_64_JUMP_SLO 0000000000000000 regget + 0
000000003fd0 000800000007 R_X86_64_JUMP_SLO 0000000000000000 atoi@GLIBC_2.2.5 + 0
The decoding of unwind sections for machine type Advanced Micro Devices X86-64 is not currently supported.
Symbol table '.dynsym' contains 11 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
1: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTab
2: 0000000000000000 0 FUNC GLOBAL DEFAULT UND printf@GLIBC_2.2.5 (2)
3: 0000000000000000 0 FUNC GLOBAL DEFAULT UND __libc_start_main@GLIBC_2.2.5 (2)
4: 0000000000000000 0 FUNC GLOBAL DEFAULT UND strcmp@GLIBC_2.2.5 (2)
5: 0000000000000000 0 NOTYPE WEAK DEFAULT UND __gmon_start__
6: 0000000000000000 0 FUNC GLOBAL DEFAULT UND regset
7: 0000000000000000 0 FUNC GLOBAL DEFAULT UND regget
8: 0000000000000000 0 FUNC GLOBAL DEFAULT UND atoi@GLIBC_2.2.5 (2)
9: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMCloneTable
10: 0000000000000000 0 FUNC WEAK DEFAULT UND __cxa_finalize@GLIBC_2.2.5 (2)
Symbol table '.symtab' contains 69 entries:
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10: 00000000000005b8 0 SECTION LOCAL DEFAULT 10
11: 0000000000000678 0 SECTION LOCAL DEFAULT 11
12: 0000000000001000 0 SECTION LOCAL DEFAULT 12
13: 0000000000001020 0 SECTION LOCAL DEFAULT 13
14: 0000000000001080 0 SECTION LOCAL DEFAULT 14
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16: 00000000000010e0 0 SECTION LOCAL DEFAULT 16
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18: 0000000000002000 0 SECTION LOCAL DEFAULT 18
19: 00000000000020a0 0 SECTION LOCAL DEFAULT 19
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25: 0000000000004000 0 SECTION LOCAL DEFAULT 25
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27: 0000000000000000 0 SECTION LOCAL DEFAULT 27
28: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
29: 0000000000001110 0 FUNC LOCAL DEFAULT 16 deregister_tm_clones
30: 0000000000001140 0 FUNC LOCAL DEFAULT 16 register_tm_clones
31: 0000000000001180 0 FUNC LOCAL DEFAULT 16 __do_global_dtors_aux
32: 0000000000004010 1 OBJECT LOCAL DEFAULT 26 completed.8061
33: 0000000000003d80 0 OBJECT LOCAL DEFAULT 22 __do_global_dtors_aux_fin
34: 00000000000011c0 0 FUNC LOCAL DEFAULT 16 frame_dummy
35: 0000000000003d78 0 OBJECT LOCAL DEFAULT 21 __frame_dummy_init_array_
36: 0000000000000000 0 FILE LOCAL DEFAULT ABS main.c
37: 0000000000000000 0 FILE LOCAL DEFAULT ABS crtstuff.c
38: 00000000000021ec 0 OBJECT LOCAL DEFAULT 20 __FRAME_END__
39: 0000000000000000 0 FILE LOCAL DEFAULT ABS
40: 0000000000003d80 0 NOTYPE LOCAL DEFAULT 21 __init_array_end
41: 0000000000003d88 0 OBJECT LOCAL DEFAULT 23 _DYNAMIC
42: 0000000000003d78 0 NOTYPE LOCAL DEFAULT 21 __init_array_start
43: 00000000000020a0 0 NOTYPE LOCAL DEFAULT 19 __GNU_EH_FRAME_HDR
44: 0000000000003f98 0 OBJECT LOCAL DEFAULT 24 _GLOBAL_OFFSET_TABLE_
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46: 0000000000001360 5 FUNC GLOBAL DEFAULT 16 __libc_csu_fini
47: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_deregisterTMCloneTab
48: 0000000000004000 0 NOTYPE WEAK DEFAULT 25 data_start
49: 0000000000004010 0 NOTYPE GLOBAL DEFAULT 25 _edata
50: 0000000000001368 0 FUNC GLOBAL HIDDEN 17 _fini
59: 0000000000004018 0 NOTYPE GLOBAL DEFAULT 26 _end
60: 00000000000010e0 47 FUNC GLOBAL DEFAULT 16 _start
61: 0000000000004010 0 NOTYPE GLOBAL DEFAULT 26 __bss_start
62: 00000000000011c9 293 FUNC GLOBAL DEFAULT 16 main
63: 0000000000000000 0 FUNC GLOBAL DEFAULT UND regset
64: 0000000000000000 0 FUNC GLOBAL DEFAULT UND regget
65: 0000000000000000 0 FUNC GLOBAL DEFAULT UND atoi@@GLIBC_2.2.5
66: 0000000000004010 0 OBJECT GLOBAL HIDDEN 25 __TMC_END__
67: 0000000000000000 0 NOTYPE WEAK DEFAULT UND _ITM_registerTMCloneTable
68: 0000000000000000 0 FUNC WEAK DEFAULT UND __cxa_finalize@@GLIBC_2.2
Histogram for `.gnu.hash' bucket list length (total of 2 buckets):
Length Number % of total Coverage
0 1 ( 50.0%)
1 1 ( 50.0%) 100.0%
Version symbols section '.gnu.version' contains 11 entries:
Addr: 0x000000000000057e Offset: 0x00057e Link: 6 (.dynsym)
000: 0 (*local*) 0 (*local*) 2 (GLIBC_2.2.5) 2 (GLIBC_2.2.5)
004: 2 (GLIBC_2.2.5) 0 (*local*) 0 (*local*) 0 (*local*)
008: 2 (GLIBC_2.2.5) 0 (*local*) 2 (GLIBC_2.2.5)
Version needs section '.gnu.version_r' contains 1 entry:
Addr: 0x0000000000000598 Offset: 0x000598 Link: 7 (.dynstr)
000000: Version: 1 File: libc.so.6 Cnt: 1
0x0010: Name: GLIBC_2.2.5 Flags: none Version: 2
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GNU 0x00000010 NT_GNU_PROPERTY_TYPE_0
Properties: x86 feature: IBT, SHSTK
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Build ID: e77046db6ef702a971f1bcda6ee429513c6ad762
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OS: Linux, ABI: 3.2.0
:::
### Write the Makefile and build it
```shell
Tomas# cat Makefile
# Compiler and flags
CC = gcc
CFLAGS = -Wall -Wextra -Iregapi/include
LIB_CFLAGS = -Wall -Wextra -Iregapi/include -fPIC
LDFLAGS = -L. -lregapi
# Source files and objects
SRC = main.c
LIB_SRC = regapi/src/regapi.c
OBJ = $(SRC:.c=.o) regapi.o
# Target executable
TARGET = hello
.PHONY: all clean
all: $(TARGET)
# Build the static library
libregapi.a: regapi.o
ar rcs $@ $^
# Build the static library
libregapi.so: regapi.o
$(CC) -s -shared -o $@ $^
# Compile the library source file
#regapi.o: $(LIB_SRC)
# $(CC) $(CFLAGS) -c $<
regapi.o: $(LIB_SRC)
$(CC) $(LIB_CFLAGS) -c $<
# Build the main executable
$(TARGET): $(OBJ) libregapi.so
#$(TARGET): $(OBJ) libregapi.a
$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
# Compile source files
%.o: %.c
$(CC) $(CFLAGS) -c $<
clean:
rm -f $(TARGET) $(OBJ) libregapi.a libregapi.so
```
## Summary
### Comparision
| Item | Type | File name | Size |
|-| -------- | -------- | -------- |
|1 |Static library | libregapi.a | 3242 |
|2 |Dynamic library | libregapi.so | 14472 |
|3 |Application w/ static library | hello | 16944 |
|4 |Appliaction w/ dynamic library | hello| 17208 |
From the table above, it is obvious to see
1. the size of the static library is smaller than the dynamic one.
2. the size of the main application with static library is 184 bytes larger than the one with dynamic library.
### Pros and cons
| | Static library | Dynamic library |
| -------- | -------- | -------- |
| App size | larger | smaller |
| Library size | smaller | larger|
| Version control | No | Yes |
| Easy to develop App | Yes | No |
|Reusable | No| Yes |
## Appendix
### Common Makefile
We write a Makefile to build the application with a static library and a dynamic library by setting the flag SHARED_LIB:
- if SHARED_LIB = 1, hello with libregapi.so
- if SHARED_LIB = 0, hello with libregapi.a
- default, SHARED_LIB = 0
```shell
#
# 'make SHARED_LIB=0' build executable file with libregapi.a
# 'make SHARED_LIB=1' build executable file with libregapi.so
# 'make clean' removes all .o, .a, .so and executable files
#
# Compiler and flags
CC = gcc
CFLAGS = -Wall -Wextra -Iregapi/include
LIB_CFLAGS = -Wall -Wextra -Iregapi/include -fPIC
LDFLAGS = -L. -lregapi
# Source files and objects
SRC = main.c
LIB_SRC = regapi/src/regapi.c
OBJ = $(SRC:.c=.o) regapi.o
# Target executable
TARGET = hello
.PHONY: all clean
all: $(TARGET)
# Build the static library
libregapi.so: regapi.o
$(CC) -s -shared -o $@ $^
ifeq ($(SHARED_LIB),1)
# Compile the library source file
regapi.o: $(LIB_SRC)
$(CC) $(LIB_CFLAGS) -c $<
# Build the main executable
$(TARGET): $(OBJ) libregapi.so
$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
TARGET = hello
.PHONY: all clean
all: $(TARGET)
# Build the static library
libregapi.a: regapi.o
ar rcs $@ $^
# Build the static library
libregapi.so: regapi.o
$(CC) -s -shared -o $@ $^
ifeq ($(SHARED_LIB),1)
# Compile the library source file
regapi.o: $(LIB_SRC)
$(CC) $(LIB_CFLAGS) -c $<
# Build the main executable
$(TARGET): $(OBJ) libregapi.so
$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
else
# Compile the library source file
regapi.o: $(LIB_SRC)
$(CC) $(CFLAGS) -c $<
# Build the main executable
$(TARGET): $(OBJ) libregapi.a
$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS)
endif
# Compile source files
%.o: %.c
$(CC) $(CFLAGS) -c $<
clean:
rm -f $(TARGET) $(OBJ) libregapi.a libregapi.so
```
Example,
```shell
Tomas# make SHARED_LIB=1
gcc -Wall -Wextra -Iregapi/include -c main.c
gcc -Wall -Wextra -Iregapi/include -fPIC -c regapi/src/regapi.c
gcc -s -shared -o libregapi.so regapi.o
gcc -Wall -Wextra -Iregapi/include -o hello main.o regapi.o libregapi.so -L. -lregapi
Tomas# ls -al
-rwxrwxr-x 1 tomas tomas 17208 十 22 22:08 hello
-rwxrwxr-x 1 tomas tomas 14472 十 22 22:08 libregapi.so
-rw-rw-r-- 1 tomas tomas 741 十 22 19:35 main.c
-rw-rw-r-- 1 tomas tomas 2576 十 22 22:08 main.o
-rw-rw-r-- 1 tomas tomas 1148 十 22 22:07 Makefile
-rw-rw-r-- 1 tomas tomas 603 十 22 21:19 Makefile.static
drwxrwxr-x 4 tomas tomas 4096 十 22 17:25 regapi
-rw-rw-r-- 1 tomas tomas 3088 十 22 22:08 regapi.o
-rw-rw-r-- 1 tomas tomas 2 十 22 21:09 reg.txt
Tomas# make
gcc -Wall -Wextra -Iregapi/include -c main.c
gcc -Wall -Wextra -Iregapi/include -c regapi/src/regapi.c
ar rcs libregapi.a regapi.o
gcc -Wall -Wextra -Iregapi/include -o hello main.o regapi.o libregapi.a -L. -lregapi
Tomas# ls -al
-rwxrwxr-x 1 tomas tomas 17208 十 22 22:08 hello
-rw-rw-r-- 1 tomas tomas 3242 十 22 22:08 libregapi.a
-rw-rw-r-- 1 tomas tomas 741 十 22 19:35 main.c
-rw-rw-r-- 1 tomas tomas 2576 十 22 22:08 main.o
-rw-rw-r-- 1 tomas tomas 1148 十 22 22:07 Makefile
-rw-rw-r-- 1 tomas tomas 603 十 22 21:19 Makefile.static
drwxrwxr-x 4 tomas tomas 4096 十 22 17:25 regapi
-rw-rw-r-- 1 tomas tomas 3088 十 22 22:08 regapi.o
-rw-rw-r-- 1 tomas tomas 2 十 22 21:09 reg.txt
```
## Reference
https://www.linkedin.com/pulse/differences-between-static-dynamic-libraries-juan-david-tuta-botero
https://bryceknowhow.blogspot.com/2014/11/linux-static-library-dynamic-library.html
https://hackmd.io/@TomasZheng/Sy6ly6JWa
https://blog.gtwang.org/programming/howto-create-library-using-gcc/
https://stackoverflow.com/questions/6562403/i-dont-understand-wl-rpath-wl
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